Microsoft has released two patches for its as-yet unreleased Windows Vista operating system - a remarkable feat, even for a company that has become synonymous with security holes.

The patches, released earlier this week - MS06-042 and 051 - fix critical flaws in Internet Explorer and the Windows kernel, and were described Tuesday in a blog posting by Vista product manager Alex Heaton.

Vista is not affected by the greatest vulnerability in this month's patches, a Windows Server service flaw that is already being exploited by some hackers but the latest patches have still raised eyebrows because Microsoft had not previously acknowledged that these bugs also affect Vista.

Incredibly, this isn't the first time Microsoft has patched Vista. In January, it released a security update for Vista Beta 1. "Beta products are not listed in the security bulletins as they are still under development and not intended to be used in production environments," said Stephen Toulouse, Microsoft's security program manager. Vista, however, will be "the first major Microsoft product release that will be serviced with security updates throughout the beta process," according to Heaton.

One Microsoft observer was not overly keen on the patch. Microsoft is setting a bad precedent by agreeing to these security updates, because it muddies the difference between supported products and those in beta test, said Russ Cooper, a senior information security analyst at Cybertrust.

He believes that Microsoft is "dead wrong to commit to providing patches of any kind for Vista beta testers, in any forum other than official beta tester channels," he said. The updates do provide Microsoft with one benefit, however, Cooper said. They pre-empt reports on security flaws in Microsoft's beta software like those issued by Symantec over the past weeks. "They're avoiding more of that stupid Symantec publicity that says that Vista has security holes," he said.